I will be very happy to ramble on on this subject at length "shortly". At
present I MUST not.
Time ... .

'To go on with' here re some of my thoughts on things solar, some of which
will be relevant. Subset with extra search terms if it looks useful.

            http://bit.ly/RMcSolar

I'd probably start off with an 'old dead almost free ' battery to get a
feel for things.

Look at wonderful Gaisma for sun data for your cityu

http://www.gaisma.com/en/location/melbourne.html

By month. KwH/m^2/day.

Variable IIIIII IVV VIVIIVIII IXX XIXII Insolation, kWh/m=B2/day6.15 5.654.=
343.07
2.12 1.661.81 2.523.40 4.605.63 6.07

 So your 20W panel optimally used with give about 20 x 1.66 =3D 33 Wh on an
average mid Winter day and 6.15 x 20 =3D 123 Wh on an average mid-Summer da=
y.

If you can store about 25 Wh of your Winter energy you'd get 2.5W over 10
hours.
IF the 250 mA is at 12V then that's about right for 1 night's operation.

The 25 Wh is about 2+ Ah of capacity so a 7Ah battery would be about 1/3
discharged by a 10 hour 250 mA load. Less deep the better, as you will know=
..

A 40 Ah or so large car battery would be discharged to about 2.5/40 =3D < 7=
%
by the same load.
How the car battery would far on 7% discharges compared to a 7Ah deep cycle
battery at 33% is TBD but

** WAIT ****

I misread the price.
At $14.90 Australian that battery is a bargain. Buy it while it's still on
special! :-)

If that's a *genuine Panasonic* AGM deep discharge 7Ah 12V it's an utter
bargain.
If its a "double flying horse", maybe not.

More anon.
Buy the battery NOW.

What price for panels?

Large (250W) panels have sold here recently for $NZ1/Watt (!!!)

Anon


    Russell




On 19 July 2013 16:17, Grant Tudor <grant.tudor@gmail.com> wrote:

> I have decided my winter project is to install some solar powered LED
> lights in my hot house so I can start growing my tomatoes earlier this
> year. I have the lights already and they draw about 250mA. For the batter=
y
> I am thinking of using a 7Ah, 12V SLA - something like this:
>
>
> http://www.rockby.com.au/catresults.cfm?imageField2.x=3D0&imageField2.y=
=3D0&stock_no=3D38696
>
> I am looking for some suggestions re charger and panels. I would like to
> look at some 20W panels - starting with 1 or 2 (increasing the number as =
I
> come up with other ideas). The panels will be mounted on a tin roof shed
> adjoining the hot house.
>
> The intent is not to just buy a solution and get someone to install, but =
to
> do some of it myself and learn a bit along the way.
>
> I am in Melbourne, Australia (in case anyone knows of some options in thi=
s
> particular location).
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.